---
title: "Need for traversing, types, Bowditch rule"
subject: "Surveying II"
chapter: 1
key: "semester_4/surveying_ii:traversing-necessity-types-bowditch"
source: https://www.bctengineer.com/q/semester_4/surveying_ii/traversing-necessity-types-bowditch
site: BCT Engineering
---

# Need for traversing, types, Bowditch rule

Surveying II · Chapter 1: Traversing

- Asked in: 2081 Chaitra, 1+1+2 marks
- Video: [Balancing of traverse using Bowditch rule](https://www.youtube.com/watch?v=hUn7pl7iZ0A) — Gayathri VG
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_4/surveying_ii/traversing-necessity-types-bowditch
- Whole chapter: https://www.bctengineer.com/md/semester_4/surveying_ii/chapter-1

## Question

Why traversing is necessary? What are the types of traverse? Explain Bowditch's rule for balancing the traverse with its assumptions.

## Short answer

Traversing is necessary as the quickest way to provide horizontal control for narrow strips and built-up areas. Types: closed (loop or link) and open traverse. Bowditch's rule distributes closing error in latitude and departure proportionally to line lengths, assuming equal precision and accidental errors.

## Answer

#### Necessity of traversing
Traversing is the quickest and cheapest way to provide horizontal control for surveys of long, narrow strips and of built-up and wooded areas, where triangulation is not practicable. It gives the coordinates of the stations, from which details are plotted and works are set out.

#### Types of traverse
- **Closed traverse:** closed loop (starts and ends at the same station) and closed link (starts and ends at known stations).
- **Open traverse:** starts at a known station and ends at an unknown one.
- By instrument and angle measurement: compass, chain, theodolite and plane table traverses; included angle, deflection angle and direct bearing methods.

#### Bowditch's rule
**Bowditch (compass) rule:** the closing error in latitude and departure is distributed among the lines in proportion to their lengths.

$$
C_L=-\Sigma L_{at}\times\frac{l}{\Sigma l},\qquad C_D=-\Sigma D_{ep}\times\frac{l}{\Sigma l}
$$

where $l$ is the length of the line and $\Sigma l$ the perimeter (or total length of the traverse).

**Assumptions:**
- Angular and linear measurements are of equal precision, and the errors are accidental (random) only.
- The error in the linear measurement of a line is proportional to $\sqrt{l}$, and the error in angular measurement is inversely proportional to $\sqrt{l}$. On these assumptions, the correction to the latitude and departure of each line works out to be proportional to its length.
- The angular misclosure has already been distributed among the angles before the rule is applied.

It is simple, and it is the most commonly used rule in plane surveying.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Traversing is mainly preferred over triangulation for:
   A. Very large open areas
   B. Long narrow strips and built-up or wooded areas where triangulation is impracticable
   C. Measuring heights only
   D. Surveys needing no coordinates
   Answer: B. It is a quick and cheap way to give horizontal control where intervisibility for triangulation is poor. (Key point: Necessity of traversing)

2. A closed link traverse is one that:
   A. Starts at a known station and ends at an unknown one
   B. Returns to its starting station
   C. Starts and ends at known stations
   D. Uses only a compass
   Answer: C. Closed traverse includes the closed loop (same start and end) and the closed link (start and end at known stations). (Key point: Types of traverse)

3. Bowditch's correction to a line is proportional to:
   A. Its latitude
   B. The angle at its start
   C. Its departure
   D. Its length
   Answer: D. Error is distributed among lines in proportion to length: C = -sum x l / sum l. (Key point: Bowditch rule)

4. Which is an assumption of Bowditch's rule?
   A. Angular and linear measurements are of equal accuracy
   B. Angles are far better than lengths
   C. Only compass angles are used
   D. Lengths are error-free
   Answer: A. Bowditch assumes equal accuracy of angles and lengths, error in a line proportional to sqrt(l), and angles balanced first. (Key point: Bowditch assumptions)

## Related in Surveying II

- [Field measurements in traversing, Bowditch rule](https://www.bctengineer.com/question.md?key=semester_4%2Fsurveying_ii%3Atraverse-field-measurements-bowditch-rule) — Surveying II, chapter 1
- [Closed/open traverse, Bowditch's rule](https://www.bctengineer.com/question.md?key=semester_4%2Fsurveying_ii%3Aclosed-open-traverse-bowditch-rule) — Surveying II, chapter 1, asked 2×
- [Bowditch balancing of link traverse XABCY](https://www.bctengineer.com/question.md?key=semester_4%2Fsurveying_ii%3Abowditch-link-traverse-xabcy) — Surveying II, chapter 1, asked 2×
- [Balancing linked traverse, transit rule](https://www.bctengineer.com/question.md?key=semester_4%2Fsurveying_ii%3Alinked-traverse-misclosure-transit-rule) — Surveying II, chapter 1, asked 2×
- [Bowditch link traverse XABCY (X 1162.510 N)](https://www.bctengineer.com/question.md?key=semester_4%2Fsurveying_ii%3Abowditch-link-traverse-xabcy-1162) — Surveying II, chapter 1, asked 2×
- [Bowditch link traverse XABCY (X 1877.51 N)](https://www.bctengineer.com/question.md?key=semester_4%2Fsurveying_ii%3Abowditch-link-traverse-xabcy-1877) — Surveying II, chapter 1

## Related in other subjects

- [Checking open traverse; Bowditch graphically](https://www.bctengineer.com/question.md?key=semester_3%2Fsurveying_i%3Aopen-traverse-check-bowditch) — Surveying I, chapter 4
- [Is balancing tank necessary: 20000 L/day spring](https://www.bctengineer.com/question.md?key=semester_5%2Fwater_supply_engineering%3Ares-k72) — Water Supply Engineering, chapter 7